As a conventional vehicle inclination detecting device, for example, there is a device shown in patent reference 1. An ultrasonic wave transmitting unit transmits an ultrasonic wave toward a ground surface (road surface). The vehicle inclination detecting device receives the ultrasonic wave reflected from the ground surface by using ultrasonic receiving units disposed at different positions. The vehicle inclination detecting device measures the time that elapses from the transmission to the reception, and computes the difference between the receiving times of the ultrasonic reception units or the phase difference between the ultrasonic waves received by the ultrasonic receiving units to detect the angle of inclination of a vehicle.
Further, as a conventional vehicle inclination detecting device, for example, there is a device shown in patent reference 2. A radio wave transmitting unit emits a radio wave toward a ground surface, and a radio wave receiving unit receives the radio wave reflected from a road surface by using two receiving antennas. A computing unit computes the phase difference between the two received signals by carrying out a combining process, and detects the angle of inclination of a vehicle.
Further, as a conventional vehicle inclination detecting device, for example, there is a device shown in patent reference 3. Two ultrasonic transmission and reception sensors are disposed in a longitudinal direction of a vehicle. An ultrasonic wave transmitting unit transmits an ultrasonic wave toward a ground surface. The vehicle inclination detecting device receives the ultrasonic wave reflected from the ground surface by using an ultrasonic receiving unit, and measures the time that elapses from the transmission to the reception. The vehicle inclination detecting device detects the angle of inclination of the vehicle from the mount space in a longitudinal direction between the ultrasonic transmission and reception sensors, the difference between the receiving times of the ultrasonic transmission and reception sensors or the phase difference between the ultrasonic waves received by the ultrasonic transmission and reception sensors, and the difference between the levels of the two ultrasonic transmission and reception sensors. The vehicle inclination detecting device determines whether the vehicle is in either a travelling state or an idle state from the vehicle speed measured by a speed sensor, and carries out an averaging process by using the angle of inclination which the vehicle inclination detecting device computes while the vehicle is travelling on a priority basis to output an average of the angle of inclination.
Further, as a conventional vehicle inclination detecting device, for example, there is a device shown in patent reference 4. A radio wave transmitting unit emits a radio wave toward a ground surface, and a radio wave receiving unit receives the radio wave reflected from the road surface by using two receiving antennas. The vehicle inclination detecting device carries out orthogonal detection on each of the received signals and the transmission signal to acquire their respective baseband signals. The vehicle inclination detecting device then derives a phase difference to detect the angle of inclination of a vehicle by carrying out an arithmetic process on the basis of the amplitude and the phase of each of these baseband signals.